IEC61499 is a new standard for modeling of distributed control systems (DCS) using function blocks. In this paper, prototype software (FBLab) which can be applied to modeling of DCS based on this standard is presented. FBLab supports the main features of the standard like different types of function blocks, interfacing with I/O and remote devices. A sample DCS example including several environmental chambers, where each of them can be considered as a local control system, has been modeled using this software. To show some of the IEC61499 features, this example has been configured as a client-server system as is demonstrated in this paper.